Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 30: POSTER: Chemical physics

CPP 30.7: Poster

Tuesday, March 8, 2005, 16:30–18:30, Poster TU D

High-resolution spectroscopy of exciton states in single light-harvesting complexes of purple bacteria — •Philipp Reichl, Jürgen Baier, Martin Richter, Silke Oellerich, and Jürgen Köhler — Experimental Physics IV, University of Bayreuth

The initial steps in bacterial photosynthesis involve the absorption of photons by light-harvesting complexes (LH1 and LH2) and subsequent transfer of the excitation energy to the reaction center.

The crystal structure of LH2 complexes shows that the chromophores are arranged in two concentric rings embedded in the protein scaffold. Chromophores in the inner ring are separated by less than 10 Å. This leads to strong coupling and the formation of delocalized exciton states, which show broad bands in the spectrum. If disorder breaks the symmetry of the arrangement, an additional narrow line (k=0 transition) can be observed in the spectrum. From the fluorescence lifetime a linewidth of 150 MHz is predicted for this transition.

In order to detect this transition we have expanded our experimental setup to include two lasers, the first for spectral localization in a wide spectral region, the second with a linewidth of 500 kHz for high-resolution scans of the k=0 transition.